gdiplus: Add GdipSaveAddImage() stub.

dlls/gdiplus/gdiplus.spec

@@ -472,7 +472,7 @@
 472 stdcall GdipRotateTextureTransform(ptr float long)
 473 stdcall GdipRotateWorldTransform(ptr float long)
 474 stdcall GdipSaveAdd(ptr ptr)
-475 stub GdipSaveAddImage
+475 stdcall GdipSaveAddImage(ptr ptr ptr)
 476 stdcall GdipSaveGraphics(ptr ptr)
 477 stdcall GdipSaveImageToFile(ptr wstr ptr ptr)
 478 stdcall GdipSaveImageToStream(ptr ptr ptr ptr)

dlls/gdiplus/image.c

@@ -4681,11 +4681,31 @@ GpStatus WINGDIPAPI GdipSaveImageToStream(GpImage *image, IStream* stream,
 
 /*****************************************************************************
  * GdipSaveAdd [GDIPLUS.@]
+ *
+ * Like GdipSaveAddImage(), but encode the currently active frame of the given image into the file
+ * or stream that is currently being encoded.
  */
 GpStatus WINGDIPAPI GdipSaveAdd(GpImage *image, GDIPCONST EncoderParameters *params)
 {
     FIXME("(%p,%p): stub\n", image, params);
-    return Ok;
+    return NotImplemented;
+}
+
+/*****************************************************************************
+ * GdipSaveAddImage [GDIPLUS.@]
+ *
+ * Encode the currently active frame of additional_image into the file or stream that is currently
+ * being encoded by the image given in the image parameter. The first frame of a multi-frame image
+ * must be encoded using the normal GdipSaveImageToStream() or GdipSaveImageToFile() functions,
+ * but with the "MultiFrame" encoding parameter set. The multi-frame encoding process must be
+ * finished after adding the last frame by calling GdipSaveAdd() with the "Flush" encoding parameter
+ * set.
+ */
+GpStatus WINGDIPAPI GdipSaveAddImage(GpImage *image, GpImage *additional_image,
+    GDIPCONST EncoderParameters *params)
+{
+    FIXME("(%p,%p,%p): stub\n", image, additional_image, params);
+    return NotImplemented;
 }
 
 /*****************************************************************************

include/gdiplusflat.h

@@ -433,6 +433,8 @@ GpStatus WINGDIPAPI GdipRemovePropertyItem(GpImage*,PROPID);
 GpStatus WINGDIPAPI GdipSaveImageToFile(GpImage*,GDIPCONST WCHAR*,GDIPCONST CLSID*,GDIPCONST EncoderParameters*);
 GpStatus WINGDIPAPI GdipSaveImageToStream(GpImage*,IStream*,
     GDIPCONST CLSID*,GDIPCONST EncoderParameters*);
+GpStatus WINGDIPAPI GdipSaveAdd(GpImage*,GDIPCONST EncoderParameters*);
+GpStatus WINGDIPAPI GdipSaveAddImage(GpImage*,GpImage*,GDIPCONST EncoderParameters*);
 GpStatus WINGDIPAPI GdipSetImagePalette(GpImage*,GDIPCONST ColorPalette*);
 GpStatus WINGDIPAPI GdipSetPropertyItem(GpImage*,GDIPCONST PropertyItem*);